Fesoterodine fumarate is the international nonproprietary name (INN) of the active principle 2-((R)-3-diisopropylammonium-1-phenylpropyl)-4-(hydroxymethyl) phenyl isobutyrate hydrogen fumarate, whose structure formula is reported hereinbelow.

Fesoterodine fumarate was approved in Europe and in the U.S.A. for the treatment of overactive bladder syndrome with the commercial name of TOVIAZ®.
Fesoterodine fumarate was described for the first time in U.S. Pat. No. 6,858,650, which reports the preparation of the active ingredient by the salification of fesoterodine with fumaric acid, according to scheme 1 reported below.

In turn, fesoterodine (also called fesoterodine base) is described in U.S. Pat. No. 6,713,464, where it is prepared starting from a deacylated precursor, (R)-feso deacyl, i.e. (R)-2-[3-(diisopropylamino)-1-phenylpropyl]-4-(hydroxymethyl)phenol, according to scheme 2 reported hereinbelow.

The preparation of (R)-feso deacyl is instead described in U.S. Pat. No. 5,559,7269.